This invention relates to expansion joints of the type utilized in highway construction wherein gaps are formed between sections, for example, during the construction of bridges. The gaps allow for expansion and contraction of the sections in response to changes in the ambient temperature.
Such bridges are also subject to relative movement in response to occurrence of seismic events. This raises particular problems because the movements occurring during such events are not predictable both with respect to the magnitude of the movements and with respect to the direction of the movements. In many instances bridges have become unusable for significant periods of time due to the fact that traffic cannot be moved across damaged expansion joints.
The difficulty in designing of such expansion joints is that when a movement component of large magnitude is applied transverse to the roadway direction, the joints are unable to resist damage. Attempts have been made to avoid this problem, as described, for example, in U.S. Pat. No. 4,674,912. This expansion joint system, which is sold by Maurer Sohne, GmbH, attempts to deal with the problem by using sliding and swiveling movements of the joint components to accommodate the non-longitudinal movements.
The "Steelflex" system offered by D. S. Brown Company utilizes a center beam which is individually attached to its own support bar. The support bars move parallel to the direction of movement of the structure.
The "Robek System" offered by Tech Star, Inc. includes modular joints designed to accommodate longitudinal movement. As with the other prior art systems, this design has not been proven effective to prevent significant damage under substantial seismic event conditions.